Gradient composite material cable cover protection structure integrating heat prevention, heat insulation and force bearing

Abstract

The invention discloses a gradient composite material cable cover protection structure integrating heat prevention, heat insulation and force bearing. The gradient composite material cable cover protection structure comprises a cable cover, a cable, a heat insulation pad and an engine shell. The cable cover is divided into a plurality of sections along the axial direction, the front section and the rear section are lapped along steps, and lapped seams are reserved. The heat insulation pad is laid between the cable and the engine shell and is tightly pressed through the bottom edge of the cable cover, and the heat insulation and sealing effects on the interior of the cable cover are achieved. The cable cover is composed of a heat protection layer, a heat insulation layer and a force bearing layer from outside to inside in the thickness direction, 2.5 D quartz fiber woven fabric, fiber cloth, a quartz net tire and a quartz fiber cloth laying layer are adopted as reinforcement bodies respectively, all the layers are sewn into a synthetic fiber prefabricated body through sewing threads, and the cable cover is obtained through composite forming of the resin transfer molding (RTM) technology and low-density hybrid phenolic resin. According to the invention, the integration of heat prevention, heat insulation and force bearing is realized without a metal force bearing part, the requirements of light weight, low cost and high reliability are met, and excellent comprehensive performance of heat prevention, heat insulation and force bearing is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of hypersonic aircraft, and in particular relates to a thermal insulation and load-bearing integrated gradient composite material cable cover protection structure. Background Art

[0002] Hypersonic vehicles generally refer to vehicles that fly entirely within the atmosphere and at speeds exceeding Mach 5. Due to their high flight speed, strong maneuverability, and difficulty in interception, they are currently the focus of spacecraft and weapons development for major powers. When a hypersonic vehicle is flying, the surface aerodynamic heating phenomenon is very serious. The surface structure needs to withstand strong aerodynamic heat loads while bearing aerodynamic forces, making the thermal protection problem of the surface of hypersonic vehicles an important issue that needs to be solved urgently.

[0003] For hypersonic missiles with metal shell engines, thermal protection measures must be taken when the missile wall cable passes through the surface of the engine shell to ensure the normal operation of the cable. A cable cover structure is often used as a cable protection cover installed on the surface of the engine shell. The cable cover structure must meet the requirements of heat insulation and aerodynamic load.

[0004] In various missile applications, the cable cover structure is generally composed of a load-bearing layer and an anti-heat insulation layer. The load-bearing layer is made of metal materials, and the anti-heat insulation layer is made of heat-resistant composite materials or heat-resistant coatings. After continuous improvement and optimization of various models, it can meet the thermal environment conditions and load-bearing requirements of missile hypersonic flight. However, in order to achieve the country's strategic goal of low-cost and large-scale application of weapons and equipment, low-cost improvement and optimization of various missile structures has become an important work content at present.

[0005] At present, the patents related to the cable cover structure of hypersonic aircraft are as follows:

[0006] (1) An adaptive thermal deformation hook-type cable cover quick installation structure (201710572323.1);

[0007] (2) Thermal deformation adaptive cable cover (201120378387.6);

[0008] (3) An aircraft cable protection device (202211313542.5);

[0009] (4) A cable cover for the outer wall of an aircraft (201220010231.7);

[0010] (5) Combined cable protective cover (201220208410.1).

[0011] For a cable cover structure composed of a heat-insulating layer and a metal shell, the two need to be processed and manufactured separately. Among them, the heat-insulating layer is formed by winding prepreg cloth, laying and hot pressing, or by using a fiber preform through the RTM process. The metal shell is formed by machining. The two are combined by bonding or mechanical connection methods, which have the disadvantages of many production processes, large structural weight, high production costs, etc. And under high-temperature conditions during flight, due to the large difference in the expansion coefficients between the heat-insulating material and the metal material, the bonding or connection interface between the heat-insulating layer and the metal shell is prone to failure separation due to thermal stress. For a cable cover with a coating sprayed on the surface of the metal shell, its weight and cost are relatively low, but it is difficult to meet the hot environment conditions of high Mach number flight. Summary of the Invention

[0012] In order to overcome the deficiencies of the prior art, the present invention provides a heat-insulating and load-bearing integrated gradient composite cable cover protection structure, including a cable cover, a cable, a heat-insulating pad, and an engine shell. The cable cover is axially divided into several sections, and the front section and the rear section are overlapped in a stepped manner, leaving an overlapping seam to eliminate the cumulative effect of thermal deformation. A heat-insulating pad is laid between the cable and the engine shell and is pressed tightly by the bottom edge of the cable cover to play a heat-insulating and sealing role inside the cable cover, preventing external hot air from entering through the installation gap between the cable cover and the engine shell. The cable cover is composed of a heat-insulating layer, a heat-insulating layer, and a load-bearing layer from the outside to the inside along the thickness direction. 2.5D quartz fiber woven fabric, fiber cloth, quartz mesh tire, and quartz fiber cloth layering are respectively used as the reinforcement bodies. Each layer is sewn into a fiber preform through suture lines and is formed by composite molding with low-density hybrid phenolic resin using the RTM process. This gradient composite cable cover structure realizes the integration of heat insulation and load-bearing without metal load-bearing parts, meets the requirements of light weight, low cost, and high reliability, and has excellent comprehensive performance of heat insulation and load-bearing.

[0013] The technical solutions adopted by the present invention to solve its technical problems are as follows:

[0014] A heat-insulating and load-bearing integrated gradient composite cable cover protection structure, including a cable cover, a cable, a heat-insulating pad, and an engine shell; the cable is laid in the inner cavity of the cable cover; the cable cover is installed on the surface of the engine shell to protect the cable from heat insulation; the heat-insulating pad is laid between the cable and the engine shell;

[0015] The cable cover is composed of a heat-insulating layer, a heat-insulating layer, and a load-bearing layer from the outside to the inside along the thickness direction; after the heat-insulating layer, the heat-insulating layer, and the load-bearing layer are laminated in a fiber state, each layer is sewn into one body through quartz fiber suture lines to form a three-dimensional fiber braid, and after pouring low-density hybrid phenolic resin, it is cured and formed;

[0016] The cable cover is axially divided into three parts: a front-end cable cover, a middle-section cable cover, and a tail-end cable cover; the middle-section cable cover is provided in multiple sections according to the total length of the cable cover; the previous cable cover and the subsequent cable cover are connected by a stepped lap joint, and a lap joint seam is reserved; the stepped lap joint means that the lap joint of the front and rear cable covers is designed in a stepped shape, with the step of the previous cable cover lapping on the upper side of the step of the subsequent cable cover, and one side of the previous cable cover at the lap joint is higher than one side of the subsequent cable cover.

[0017] The heat insulation pad is laid on the surface of the engine housing, and both side edges are pressed by the bottom sealing groove of the cable cover, playing a sealing role to prevent external hot air flow from entering the interior of the cable cover through the installation gap between the cable cover and the engine housing, so that the cable cover, the heat insulation pad and the engine housing form a sealed protection structure.

[0018] Preferably, the anti-heat layer is composed of a 2.5D quartz fiber braid, with a thickness of 20% - 30% of the total thickness of the cable cover, playing an anti-ablation role.

[0019] Preferably, the heat insulation layer is laminated by a combination unit of fiber cloth and quartz mesh tire, with a density of 0.2 - 0.5 g / cm3 and a thickness of 50% - 70% of the total thickness of the cable cover, playing a heat insulation role.

[0020] Preferably, the load-bearing layer is laminated by quartz fiber cloth, with a thickness of 10% - 20% of the total thickness, playing a load-bearing role.

[0021] Preferably, the width of the lap joint seam is 1 mm ± 0.2 mm.

[0022] Preferably, the step height is 0.4 - 0.8 mm.

[0023] Preferably, the cross-section of the cable cover is in an inverted U shape and is installed on the surface of the engine housing, and sealing grooves are provided on the inner bottom surface of the waist lines on both sides of the cable cover.

[0024] Preferably, there is a certain gap between the cable and the surface of the heat insulation pad and the inner wall of the cable cover to avoid structural heat transfer.

[0025] Preferably, the heat insulation pad is made of silica aerogel material.

[0026] The beneficial effects of the present invention are as follows:

[0027] 1. A material and structure solution for an integrated anti-heat and load-bearing composite cable cover is designed, without a metal load-bearing layer, reducing the structural weight and eliminating the risk of separation between the anti-heat material and the metal layer;

[0028] 2. A cable cover material composition scheme is proposed, including a heat protection layer, a heat insulation layer, and a load-bearing layer; the specific materials and combination ratios of each layer are given, and this combination and ratio can meet the requirements of heat protection, heat insulation, and load-bearing integration for the cable cover. By means of integrated near-net shape forming, the number of processes is reduced, and the cost and structural weight are lowered.

[0029] 3. A cable cover structure is proposed, which includes a front-end cable cover, a middle-section cable cover, and a tail-end cable cover. The three parts are connected by a smooth stepped lap joint method, and a lap joint seam is reserved; this can reduce the influence of thermal deformation, prevent the generation of reverse steps, and prevent hot air flow from entering through the butt joint seam and affecting the cable.

[0030] 4. A high-temperature resistant aerogel pad is used as the heat insulation pad between the cable and the engine housing, and it also acts as a sealing pad, playing a certain sealing role inside the cable cover. Description of the Drawings

[0031] Figure 1 It is a cross-sectional view of the protection structure of the present invention;

[0032] Figure 2 It is a cross-sectional view of the lap joint method of the protection structure of the present invention.

[0033] Among them, 1. Cable cover, 2. Cable, 3. Heat insulation pad, 4. Engine housing; 1-1. Heat protection layer, 1-2. Heat insulation layer, 1-3. Load-bearing layer. Detailed Embodiment

[0034] The present invention will be further described below in conjunction with the drawings and embodiments.

[0035] Aiming at the problems of large structural weight, many processes, high cost, and easy separation existing in the cable cover composed of a heat protection layer and a metal housing, based on the existing technology, the present invention proposes a heat protection, heat insulation, and load-bearing integrated gradient composite material cable cover structure, which does not require a metal load-bearing layer and eliminates the risk of easy separation between the heat protection layer and the metal load-bearing layer. The key technologies for the development of the heat protection, heat insulation, and load-bearing integrated cable cover structure include heat protection and insulation materials that meet the requirements of the hypersonic thermal environment, while also taking into account the structural load-bearing requirements; heat protection, heat insulation, and load-bearing integrated composite material forming technology; lightweight and low-cost requirements.

[0036] Quartz fiber fabrics with different forms and densities are laminated and sewn into fiber preforms, giving play to the characteristics of different quartz fiber fabrics in terms of ablation resistance, heat insulation, and high strength. After being compounded with a low-density hybrid phenolic resin, a structural material with ablation resistance, heat protection and insulation, low density, and a certain load-bearing capacity is achieved. Considering from the aspects of reducing raw material costs, reducing processes, and lowering the preparation process costs, the cable cover is formed by the RTM process with near-net shape.

[0037] The present invention is designed based on the following ideas:

[0038] a) It is mainly used for the cable cover structure of hypersonic aircraft, and is designed in terms of lightweight, low cost, and integrated ablation resistance and load-bearing under medium and high heat flux conditions.

[0039] b) Instead of using the metal load-bearing layer in the traditional cable cover structure, a composite material is used as the load-bearing layer, which can be integrally formed with other layers, reducing parts and processes, lowering costs, and eliminating the risk of separation between the thermal protection composite material and the metal load-bearing layer;

[0040] c) Adopt a composite material structure solution for thermal insulation and load-bearing integration. Through measures such as material selection, optimization design of thermal insulation performance and mechanical properties, optimization design between layers, and optimization of the forming process, while achieving one-time integral forming of the structure, it meets the requirements of ablation resistance, heat insulation, and load-bearing.

[0041] d) Conduct a thermal deformation release structure design for the cable cover to avoid damage to the cable cover caused by thermal deformation of the composite material during high-speed aerodynamic heating.

[0042] The present invention mainly solves: (1) reducing the structural weight and manufacturing cost; (2) solving the risk of separation between the thermal protection layer of the composite material and the metal load-bearing layer; (3) improving the thermal insulation performance while reducing the influence of thermal deformation; (4) solving the problem of the connection sealing between the cable cover and the engine housing.

[0043] A thermal insulation and load-bearing integrated gradient composite material cable cover protection structure includes a cable cover, a cable, a heat insulation pad, and an engine housing. The cable cover is installed on the surface of the engine housing to provide thermal insulation protection for the cable, and the heat insulation pad is laid between the cable and the engine housing.

[0044] The cable cover is composed of a thermal protection layer, a heat insulation layer, and a load-bearing layer from outside to inside along the thickness direction. After the thermal protection layer, the heat insulation layer, and the load-bearing layer are laminated in a fiber state, each layer is sewn into one body by quartz fiber suture lines to form a three-dimensional fiber braid, and then cured by pouring low-density hybrid phenolic resin. The thermal protection layer is composed of a 2.5D quartz fiber braid, with a thickness of 20% - 30% of the total thickness, mainly playing the role of ablation resistance; the heat insulation layer is laminated by a combination unit of fiber cloth and quartz mesh tire, with a density of 0.2 - 0.5 g / cm3 and a thickness of 50% - 70% of the total thickness, mainly playing the role of heat insulation; the load-bearing layer is laminated by quartz fiber cloth, with a thickness of 10% - 20% of the total thickness, mainly playing the role of load-bearing. Each layer is sewn into a three-dimensional fiber braid by quartz fiber suture lines and cured by the RTM process using low-density hybrid phenolic resin, which not only meets the requirements of thermal insulation, but also has a certain stiffness and strength, ensuring the overall stiffness and strength of the composite material cable cover structure without the need for a metal load-bearing housing.

[0045] Quartz fiber cloth has excellent ablation resistance and good mechanical properties. However, if it is completely composed of quartz fiber cloth, it not only has a high density and large weight, but also has very poor interlayer bonding performance, and is prone to peeling or delamination under the action of hypersonic hot air flow. Therefore, using 2.5D quartz woven fabric as the heat protection layer on the surface of the cable cover has the common advantages of ablation resistance and anti-peeling. The heat insulation layer adopts a combination of fiber cloth and low-density quartz fiber mesh, which has the advantages of low cost, low density and heat insulation. The load-bearing layer is located in the innermost layer of the cable cover, with less ablation resistance requirements, and quartz fiber cloth with higher mechanical properties can be used to play a better load-bearing role. Each layer is laminated in a predetermined order and stitched together by sutures to form an integral cable cover preform structure. Then, the preform is placed in the inner cavity of a mold manufactured based on the outer shape of the cable cover. After sealing, phenolic resin is pressure-injected, and then placed in an oven for curing. After meeting the curing and forming conditions, the mold is removed, and the nano-porous gradient composite cable cover is taken out. This method belongs to the RTM process in composite material forming. The obtained product is formed with near-net dimensions, and no machining is required on the inner and outer surfaces, reducing the machining process and preparation cycle and lowering the cost.

[0046] The cable cover is divided into several sections along the axial direction, including three parts: the front-end cable cover, the middle-section cable cover and the tail-end cable cover. Among them, the middle-section cable cover can be set to 1 - 5 sections according to the total length of the cable cover. The front cable cover and the rear cable cover are connected by a stepped lap joint, and a lap joint seam is reserved. The width of the lap joint seam is 1mm ± 0.2mm. The stepped lap joint means that the lap joint of the front and rear cable covers is designed in a stepped shape. The front cable cover steps on the upper side of the steps of the rear cable cover, and one side of the front cable cover at the lap joint is higher than one side of the rear cable cover. The step height is 0.4 - 0.8mm.

[0047] There are mainly three advantages of using the stepped lap joint method: (1) Set the stepped lap joint in the structure in advance to prevent uneven ablation on the surface of the cable cover caused by hypersonic hot air flow and generate reverse steps. Once the reverse steps are generated, the ablation situation will further deteriorate and deepen, bringing catastrophic risks to the structure. (2) Reserve a certain gap at the lap joint to adapt to the influence of thermal deformation; (3) Use a Z-shaped lap joint gap to prevent hot air flow from directly entering the inside of the cable cover and affecting the cable.

[0048] The cross-section of the cable cover is inverted U-shaped and is installed on the surface of the engine housing. Sealing grooves are provided on the inner bottom surface of the waistlines on both sides of the cable cover.

[0049] The heat insulation pad is laid on the surface of the engine housing, and both side edges are pressed by the bottom sealing grooves of the cable cover, playing a sealing role to prevent external hot air flow from entering the inside of the cable cover through the installation gap between the cable cover and the engine housing, so that the cable cover, the heat insulation pad and the engine housing form a sealed protective structure.

[0050] The cable is laid in the inner cavity of the cable cover and on the surface of the heat insulation pad, and there is a certain gap between the cable and the inner wall of the cable cover to avoid structural heat transfer.

[0051] The heat insulation pad material has the characteristics of high temperature resistance, heat insulation and sealing.

[0052] The heat insulation pad is made of silica aerogel material.

[0053] Embodiment:

[0054] Refer to Figure 1 — Figure 2 One of the implementation schemes of the integrated gradient composite material cable cover protection structure for heat insulation and load bearing provided by the present invention includes a cable cover 1, a cable 2, a heat insulation pad 3, and an engine housing 4; the cable cover includes: a heat protection layer 1-1, a heat insulation layer 1-2, and a load bearing layer 1-3.

[0055] The engine housing 4 is a conventional solid rocket engine housing;

[0056] The cable cover 1 is composed of a heat protection layer 1-1, a heat insulation layer 1-2, and a load bearing layer 1-3 from the outside to the inside along the thickness direction, and all are nano-porous fiber reinforced resin matrix composites.

[0057] The fiber reinforcement of the heat protection layer adopts a 2.5D quartz fiber braid, which mainly plays an ablation resistance role and can be prepared by publicly known techniques in the field. The thickness of the heat protection layer is specifically set by those skilled in the art according to actual needs.

[0058] The recommended thickness of the heat protection layer is 20%-30% of the total thickness.

[0059] The fiber reinforcement of the heat insulation layer is laminated by combining a fiber cloth and a quartz mesh tire as a unit layer. Due to the low density and low thermal conductivity characteristics of the quartz mesh tire, it mainly plays a heat insulation role. The specific type of fiber cloth (such as quartz fiber cloth, high silica oxygen fiber cloth, basalt fiber cloth, etc.), the number of layers, and the number of quartz mesh tire layers are selected by those skilled in the art according to actual needs.

[0060] In this embodiment, the fiber cloth in the heat insulation layer is high silica oxygen fiber cloth, combined with the quartz mesh tire, which can take into account the advantages of low cost, low density and low thermal conductivity.

[0061] In this embodiment, the density of the fiber cloth and the quartz mesh tire in the heat insulation layer is 0.2-0.5 g / cm3.

[0062] The recommended thickness of the heat insulation layer is 50%-70% of the total thickness.

[0063] The fiber reinforcement of the load bearing layer is composed of laminated fiber cloth.

[0064] The fiber cloth of the fiber reinforcement of the load bearing layer is quartz fiber cloth, and the recommended thickness is 10%-20% of the total thickness.

[0065] After the heat-proof layer, heat-insulating layer and load-bearing layer are laminated in a fibrous state, they are sewn into one body with quartz fiber suture lines to form a three-dimensional fiber braid. Then, after being placed in a closed mold, phenolic resin is poured, and finally it is placed in an oven for curing and forming. This process can be achieved through the RTM process publicly available in the field. When forming the cable cover by using this process, no machining is required on both the inner and outer surfaces, reducing the production process.

[0066] The phenolic resin is a low-density hybrid phenolic resin. The nano-porous composite material obtained by compounding with fibers has the advantages of low density, high heat insulation and high temperature resistance, etc., and can be prepared through the organic-inorganic hybridization technology publicly available in the field.

[0067] The cable cover is axially divided into several sections. The front section of the cable cover and the rear section of the cable cover are connected by a stepped lap joint, and a lap joint seam is reserved.

[0068] The stepped lap joint means that the lap joint between the front section of the cable cover and the rear section of the cable cover is designed in a stepped shape and overlaps with each other. Among them, the step of the front section of the cable cover overlaps on the upper side of the step of the rear section of the cable cover, forming a Z-shaped lap joint seam, and at the lap joint seam, the surface on the front side is higher than the surface on the rear side.

[0069] The width of the lap joint seam is 1mm ± 0.2mm. After the cable cover is installed, high-temperature resistant silicone rubber is filled inside the gap to play a sealing role.

[0070] The surface of the cable cover on the front side is 0.4 - 0.8mm higher than the surface of the cable cover on the rear side.

[0071] The cross-section of the cable cover is U-shaped and is installed upside down on the surface of the engine housing. Notched sealing grooves are provided on the inner bottom surface of the waist lines on both sides of the cable cover.

[0072] The heat-insulating pad is laid on the surface of the engine housing. The two side edges of the heat-insulating pad just fit into the notched sealing grooves provided on the inner bottom surface of the waist lines on both sides of the cable cover, and the heat-insulating pad is pressed tightly by the cable cover to play a sealing role, preventing hot air flow from entering the interior through the installation gap between the cable cover and the engine housing, so that the cable cover, the heat-insulating pad and the engine housing form a sealed protective structure.

[0073] The cable is laid in the inner cavity of the cable cover and on the surface of the heat-insulating pad. There is a certain gap between the cable and the cable cover. There is a layer of heat-insulating pad between the cable and the engine housing, and it is in a good heat-insulating state.

[0074] The heat-insulating pad has the characteristics of high temperature resistance, heat insulation and sealing, etc.

[0075] The heat-insulating pad is made of silica aerogel material.

Claims

1. An integrated anti-heat-insulation and load-bearing gradient composite cable cover protection structure, characterized in that It includes a cable cover, a cable, a heat insulation pad and an engine housing; the cable is laid in the inner cavity of the cable cover; the cable cover is installed on the surface of the engine housing to provide heat and insulation protection for the cable; the heat insulation pad is laid between the cable and the engine housing; The cable cover is composed of a heat protection layer, a heat insulation layer and a load-bearing layer from outside to inside in the thickness direction; after the heat protection layer, the heat insulation layer and the load-bearing layer are laminated in a fiber state, each layer is sewn into one body by a quartz fiber suture to form a three-dimensional fiber braid, and after being infused with low-density hybrid phenolic resin, it is cured and formed; The cable cover is axially divided into three parts: a front-end cable cover, a middle-section cable cover and a tail-end cable cover; the middle-section cable cover is set in multiple sections according to the total length of the cable cover; the previous section of the cable cover and the next section of the cable cover are connected by a smooth step overlap, and a lap joint is reserved; the smooth step overlap means that the lap joint of the previous and next sections of the cable cover is designed in a step shape, with the step of the previous section of the cable cover lapping on the upper side of the step of the next section of the cable cover, and one side of the previous section of the cable cover at the lap joint is higher than one side of the next section of the cable cover; The heat insulation pad is laid on the surface of the engine housing, and both side edges are pressed by the bottom sealing grooves of the cable cover, playing a sealing role to prevent external hot air flow from entering the inside of the cable cover through the installation gap between the cable cover and the engine housing, so that the cable cover, the heat insulation pad and the engine housing form a sealed protection structure.

2. The anti-heat-insulating and load-bearing integrated gradient composite cable cover protection structure according to claim 1, characterized in that The heat protection layer is composed of a 2.5D quartz fiber braid, with a thickness of 20% - 30% of the total thickness of the cable cover, playing an anti-ablation role.

3. The integrated gradient composite cable cover protection structure for heat insulation and load bearing according to claim 1, characterized in that The heat insulation layer is laminated by a combination unit of fiber cloth and quartz mesh tire, with a density of 0.2 - 0.5 g / cm3 and a thickness of 50% - 70% of the total thickness of the cable cover, playing a heat insulation role.

4. The anti-heat-insulating and load-bearing integrated gradient composite cable cover protection structure according to claim 1, characterized in that, The load-bearing layer is laminated by quartz fiber cloth, with a thickness of 10% - 20% of the total thickness, playing a load-bearing role.

5. The integrated anti-heat-insulation and load-bearing gradient composite material cable cover protection structure according to claim 1, characterized in that, The width of the lap joint is 1mm ± 0.2mm.

6. The integrated gradient composite cable cover protection structure for heat insulation and load bearing according to claim 1, characterized in that, The step height is 0.4 - 0.8mm.

7. A heat-insulating and load-bearing integrated gradient composite cable cover protection structure according to claim 1, characterized in that, The cross-section of the cable cover is in an inverted U shape and is installed on the surface of the engine housing. Sealing grooves are provided on the inner bottom surface of the waistlines on both sides of the cable cover.

8. The integrated heat-insulating and load-bearing gradient composite material cable cover protection structure according to claim 1, characterized in that, There is a certain gap between the cable and the surface of the heat insulation pad and the inner wall of the cable cover to avoid structural heat transfer.

9. The integrated gradient composite cable cover protection structure for heat insulation and load bearing according to claim 1, characterized in that The heat insulation pad uses silica aerogel material.

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